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Bouras Fawzi Al-Mukhtar Muzahim Tapsoba Nouffou Belayachi Naima Sabio Serge Beck Kévin Martin Mylène 《Geotechnical and Geological Engineering》2022,40(4):2033-2049
Geotechnical and Geological Engineering - An investigation performed on the interactions of silty soil treated with cement or lime demonstrates the strong relationship between microstructural... 相似文献
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This paper presents the results of an ageing test based on cycles of wetting–drying of a French building limestone named tuffeau. During 3 years, 50 complete wetting–drying cycles with pure distilled water were carried out on the side of a cylindrical sample. The characterization of the stone shows that the ageing test applied induces changes in the surface appearance, with the formation of a patina with decrease in porosity and mineralogical changes due to dissolution, transport, and recrystallization of the dissolved mineralogical component of the rock as calcite. The decrease in the imbibition kinetics confirms the alteration of the tested stone sample. After 50 wetting–drying cycles, imbibition coefficients are almost halved. This alteration is not homogeneous as the patina covers only some sections of the exposed surface of the stone. On the well-formed parts of the patina with a brownish and varnished aspect, which represent about 20 % of the total surface, measurements show a decrease in porosity and roughness of about 25 %. The physico-chemical characterization shows that the patina formed in the laboratory is fully comparable to natural patina observed on monuments built of tuffeau. 相似文献
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Asaad Al-Omari Xavier Brunetaud Kevin Beck Muzahim Al-Mukhtar 《Environmental Earth Sciences》2014,71(9):3977-3989
This work consists in estimating the role of climatic conditions in the degradation of two French limestones, tuffeau and Richemont stone, used in the construction and the restoration of the Castle of Chambord, the largest castle in the Loire Valley, France. Meteorological data, air temperature, air relative humidity and rainfall were statistically analysed in combination with stone data from thermal–humidity sensors inserted into the walls. The climatic conditions of the surrounding area were described to assess their role in enhancing the degradation of the stones through three weathering processes: thermal stress, condensation and freezing–thawing. The damage risks due to the weathering processes were taken into account not only through the bulk effects on the stone surfaces, but also their effects were extended to investigate the damage that occurs within the porous structure of the stone. Field observations showed that the main patterns of degradation affecting the stones of the castle are biological colonization and stone detachment in the form of stone spalling and exfoliation. The results of the analysis show that there is no risk of damage to the stones due to thermal stress. Moreover, the two stones experience similar overall trends against freezing–thawing processes. Finally, this study clearly highlights the important role of condensation in the degradation of the stones of the castle. 相似文献
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Sarah Janvier-Badosa Kévin Beck Xavier Brunetaud Muzahim Al-Mukhtar 《Environmental Earth Sciences》2014,71(11):4751-4759
The main cause of degradation in tuffeau, a soft siliceous and clayey limestone extensively used in the construction of the castles of the Loire Valley in France, is scaling. The most damaging form of weathering is spalling. Over time, a plaque several centimetres in thickness gradually forms under the stone surface and eventually falls away, leaving the resulting new surface powdered. Hypotheses regarding the initiation and development of such degradation have not yet met scientific consensus. The objective of the present paper is to improve existing knowledge of scaling degradation by analysing in situ samples representing different stages of the same degradation process. The analysis of the stones at the Castle of Chambord, revealed the presence of gypsum (CaSO4·2H2O), mainly located in cracks parallel to the stone surface. This gypsum was then studied in terms of its crystal morphology and distribution with depth. For comparison purposes, another form of scaling identified at the Castle of Chambord but rarely studied, flaking, was also examined. A first attempt at explaining the origin and formation of the observed gypsum in both scaling processes was conducted by interacting and comparing the characterisation results with historical and environmental data. 相似文献
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Soil erosion by water is one of the most widespread forms of soil degradation in Europe. There are many undesirable consequences of soil erosion due to water such as loss of water storage capacity in reservoirs and transfer of pollutants from farmland to water bodies. The objectives of this study were to calibrate and validate the Water Erosion Prediction Project watershed model (WEPP 2012.8) in the Bautzen dam catchment area with monthly and daily single events for runoff and sediment yield. This is to our knowledge the first study using WEPP in Germany. The catchment (310 km2) was subdivided into small sub-catchments with an area of <260 ha as recommended in WEPP. A sensitivity analysis revealed that the runoff is highly sensitive to the effective hydraulic conductivity in Bautzen, whereas the sediment yield is highly sensitive to rill erodibility, critical shear stress, and to the effective hydraulic conductivity as well. All these parameters were initially calculated using WEPP’s built-in equations and parameters, which, however, produced very poor results for both runoff and sediment yield. Therefore, the model was calibrated for 2 years (2005–2007) and validated for another 2 years (2008–2009) against monthly measurements, in addition to 14 daily single events from the calibration period and 2010. The monthly results were compared with the monthly measurements on the basis of a continuous simulation. Results of calibration and validation periods show a satisfactory performance of WEPP with a determination coefficient R 2 above 0.6 and Nash–Sutcliffe efficiency coefficients above 0.50 for runoff and sediment yield. Thus, the model could be used to simulate runoff and sediment yield, and used in scenario studies in the Bautzen dam catchment area. 相似文献
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Accelerated weathering tests on two highly porous limestones 总被引：3，自引：0，他引：3
A major cause of weathering of building and historic monuments constructed using limestones is associated with the salt crystallization.
This may typically occur at the surface (due to efflorescence) or in subsurface layers while limestones are drying. Due to
this reason structural damage or material loss (granular disintegration, flaking, contour scaling) may occur. In this paper,
imbibition-drying cycles are carried out with pure water and solutions of NaCl with different concentrations to simulate the
weathering effect on two limestones with similar total porosity values. The imbibition kinetics of these limestones was significantly
influenced by the number of applied imbibition-drying cycles. In addition, imbibition kinetics was also dependent on the concentration
of salt solutions, the mineralogical composition as well as on the pore-size distribution of these two stones. The structural
and textural modifications that arise in the limestones due to the influence of imbibition characteristics of drying cycles
are qualitatively confirmed by scanning electronic microscope (SEM) and quantitatively with helium pycnometry measurements. 相似文献
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Xavier Guillot Muzahim Al-Mukhtar Faiza Bergaya Jean-Marie Fleureau 《Comptes Rendus Geoscience》2002,334(2):105-109
Porosity measurements on a clay material, carried out through various microscopic techniques, show a significant difference with the total porosity macroscopically estimated. Analyses have allowed to assign this difference, whose importance is linked to the hydromechanical stresses sustained by the material, to microporous spaces lower than 2 nm and to closed pore volumes, not accessible by the used techniques. Besides, the role of the drying methods of samples, which do not allow the removal of a part of the water, is highlighted. Its elimination would lead to irreversible microtextural modifications, prejudicial to the understanding of the macroscopic behaviour of the material. To cite this article: X. Guillot et al., C. R. Geoscience 334 (2002) 105–109. 相似文献
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Formulation and characterization of an appropriate lime-based mortar for use with a porous limestone
Several studies have shown that the degradation of architectural monuments constructed using Tuffeau stones from Val de Loire region of France over a period of time are often related to use of mortars that are not compatible with the Tuffeau stones. For this reason, it is important to ensure physico-chemical compatibility between Tuffeau and the mortar. To alleviate differences in compatibility characteristics, a mortar is prepared from hydrated lime and aggregates obtained from the crushing of Tuffeau stone and used in this study. The key parameters that influence the strength and durability characteristics such as mechanical resistance, water transfer properties, and physico-chemical properties were identified and studied. Based on these studies, recommendations are offered for the preparation of a more compatible mortar that can be used in the construction and restoration of monuments using Tuffeau stone. 相似文献
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